U.S. officials confirmed on Tuesday that an American MQ-9 Reaper drone destroyed a Russian-made T-72 battle tank in Syria on Sunday, after U.S. special operations troops and their Syrian allies came under attack by forces supporting dictator Bashar Assad.

“The tank had been maneuvering with coordinated indirect fire on a defensive position occupied by Syrian Democratic Forces and Coalition advisers.

According to Central Command, the pro-regime forces involved in Sunday’s incident were from the same group that attacked U.S. special operators and Syrian fighters on February 7 and 8.

The Russians claim a handful of Russian “paramilitary contractors” were killed in the battle, while the Syrian government says U.S. troops and their allies killed almost a hundred Russians.

Mattis said the Russians told American officials there were no Russian forces involved in the attack, even though Russians have now been discovered among the dead.